There are many applications in which it is desirable to utilize a single primary electrochemical cell, such as a cylindrical electrochemical cell, which is capable of operating at one of several different discharge rates, for example, at one of three different discharge rates. It may also be a requirement that the cell operate at very low temperatures, for example, down to -40.degree. C. A typical application for a cell of the above character might utilize the different values of output voltages corresponding to the different discharge rates to power one or more loads on a selective basis.
Electrochemical cells capable of high-rate (greater than 1 mA/cm.sup.2), low-temperature (to -40.degree. C.) operation have been described in detail in U.S. Pat. No. 4,284,691, in the names of Franz Goebel and William T. McHugh, and in U.S. Pat. No. 4,309,819, in the name of Franz Goebel. In each of these patents, a cylindrical electrochemical cell is described including a battery stack disposed within a cylindrical metal housing of the cell together with an electrolytic solution. The battery stack comprises a large number of generally circular, annular-shaped electrode components superimposed on each other in a single vertical stacked array relative to the housing and relative to a central, elongated, cylindrical, metal terminal member which extends completely through the battery stack and is encircled by the battery stack components. The components of the battery stack include a plurality of anode structures and a plurality of carbon current electrode/separator assemblies arranged in the array in alternation with the anode structures. Each of the anode structures includes a metal disc, for example, of lithium, and a contact member secured to the disc and in physical and electrical contact with both the disc and the central terminal member. Each of the carbon current collector electrode/separator assemblies includes a pair of carbon/fiberglass cathode structures physically adjacent to opposite sides of a metal (e.g., nickel) current collector disc. These latter components have central openings of a size to space, or electrically isolate, the components from the central terminal member. The current collector disc is of a size and configuration so as to make direct physical and electrical contact with the interior wall of the housing of the cell.
The electrochemical cells as briefly described hereinabove and in the aforementioned patents are highly suitable for a wide range of applications requiring high-current drain, low-temperature operation. However, each of the cells as described in the patents is capable of operating within a narrow range of discharge rates. Thus, if a particular application requires the availability of several different selective discharge rates, a cell as described in the aforementioned patents does not satisfy this requirement.